Refactor validate modes, fix benchmark report and IPMI power

- Replace diag level 1-4 dropdown with Validate/Stress radio buttons
- Validate: dcgmi L2, 60s CPU, 256MB/1p memtester, SMART short
- Stress: dcgmi L3 + targeted_stress in Run All, 30min CPU, 1GB/3p memtester, SMART long/NVMe extended
- Parallel GPU mode: spawn single task for all GPUs instead of splitting per model
- Benchmark table: per-GPU columns for sequential runs, server-wide column for parallel
- Benchmark report converted to Markdown with server model, GPU model, version in header; only steady-state charts
- Fix IPMI power parsing in benchmark (was looking for 'Current Power', correct field is 'Instantaneous power reading')

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

audit/internal/platform/benchmark_test.go

@@ -137,8 +137,9 @@ func TestRenderBenchmarkReportIncludesFindingsAndScores(t *testing.T) {
 	for _, needle := range []string{
 		"Executive Summary",
 		"GPU 0 spent measurable time under SW power cap.",
-		"Composite score: 1176.00",
-		"fp16_tensor: 700.00 TOPS",
+		"1176.00",
+		"fp16_tensor",
+		"700.00",
 	} {
 		if !strings.Contains(report, needle) {
 			t.Fatalf("report missing %q\n%s", needle, report)
@@ -164,7 +165,7 @@ func TestRenderBenchmarkReportIncludesTerminalChartsWithoutANSI(t *testing.T) {
 	})
 
 	for _, needle := range []string{
-		"Terminal Charts",
+		"Steady-State Charts",
 		"GPU 0 Steady State",
 		"GPU 0 chart",
 		"42┤───",